1. Field of the Invention
The present invention relates to information processing apparatuses and methods therefor. Specifically, the present invention relates to processing of template data for use in determining (designing) the size of an implant (artificial bone) before embedding the implant into a human body, and in particular, to template data processing in the field of orthopedics.
2. Description of the Related Art
In the case of bone resection in surgery in medical fields such as orthopedics, implants, e.g., artificial bones, are used. In many instances, standard sized/shaped implants cannot be used and specially designed implants tailored to a particular patient's physique are required. Typically, a standard model is prepared, from which the implant for a particular patient is re-shaped.
When the standard model is selected, the following operations (1) and (2) are typically performed:    (1) An X-ray image formed by X-ray imaging is output onto a film; and    (2) The obtained film is superposed onto a transparent template sheet modeling an edge shape of a standard model. The transparent template sheet is then visually confirmed concerning the degree of conformity in shape between the standard model and the affected area.These operations allow determination of the size of an implant that can fit the affected area.
In recent years, with widespread use of digital X-ray imaging apparatuses, a diagnosis can be made by inputting X-ray images formed by an X-ray imaging apparatus into a terminal device, such as a personal computer, and displaying the input digital images on a high definition monitor. In this environment, determination of an implant size is done using the following operations (1) and (2):    (1) A template sheet is captured as digital information (template data) by using an image scanning apparatus such as a scanner; and    (2) The captured template data is displayed on an X-ray digital image in overlay form on a monitor, and the displayed template data is used to determine an implant size. Japanese Patent Laid-Open No. 2002-85434 discloses a method for selecting a standard model by using a digital X-ray imaging apparatus.
However, regarding an X-ray image formed by the X-ray imaging apparatus, in general, an actually formed X-ray image is approximately 10% larger in size than an object because, in image formation, a distance between an X-ray tube and a sensor differs from a distance between the X-ray tube and a patient. There are many template sheets created in which the enlargement factor is considered. When an image scanning apparatus, such as a scanner, scans a template sheet, or in processing after the image scanning apparatus scans a template sheet, the scanning resolution may change. Thus, it is not guaranteed that the X-ray image and the template data are equal in enlargement factor.
An example of a template sheet is illustrated in FIG. 1. A template sheet 11 includes plural types of standard model data items 12 indicating the sizes and shapes of implants, size representations 13 representing the sizes of the standard model data items, a value representation 14 representing an enlargement factor of the template sheet 11, and a scale 15 for measuring the enlargement factor.
The template sheet 11 is created considering a magnification of 10%. Thus, the scale 15 has an actual length of 11 centimeters when the scale 15 is actually measured with a ruler. When the template sheet 11 is digitized by an image scanning apparatus, such as a scanner, the resolution of the digitized template data may change in the middle of digitization. A change in resolution changes a preset enlargement factor and an enlargement factor of an image actually displayed on a monitor. Determination of an implant size by using template data having a changed enlargement factor leads to determination of a wrong implant size, thus resulting in a decrease in diagnosis efficiency of a doctor. Therefore, it is very important to maintain accuracy of an enlargement factor of template data.